Artificial blood substitutes containing liquid perfluorochemicals, high molecular weight polyols, and hydroxyethyl starch have been successful for total blood replacement in animals. Furthermore, bloodless rats obtained in this manner can live for 24 hours in 10% carbon monoxide, proving beyond any reasonable doubt that the substitute is completely responsible for sustaining the life of the animal. The proposed research will extend these studies to new kinds of perfluorochemicals and formulations, and also to new animal species. Included will be a new series of heteroatom-free perfluorocompounds since they appear to form very stable emulsions in contrast to previously tested materials . The physiology, histology, nutrition, and biochemistry of bloodless animals will be investigated in detail. The fate of the perfluorochemicals and other components of the artiificial blood will be ascertained. Further experiments will be carried out with bloodless animals to determine the lowest level of oxygen still compatible with normal performance. A more detailed study of the effects of carbon monoxide on bloodless and perfluorochemical-treated normal animals will be carried out. The use of the artificial substitutes in organ perfusion, in tissue culture systems, and for hyperbaric experiments will be investigated.